For sure. Any trip beyond 1 week in Japan is totally worth buying the JR pass.
It may seem expensive, but it will save you money.
I imagine you'll go from Tokyo to Osaka, maybe go to Hiroshima in between. For all of that, you can use the JR pass even for the Shinkansen (bullet trains), which makes this worth 2 times: One for your money and one for your time.
However, if you only want to go by bus, the JR pass is not worth it for everyday transportations such as train and metro. You can use your JR pass in any JR stations, which there are many, but traveling around Tokyo, you will be using a lot the metro system as well, which does not take the JR pass.
My recommendation is: if you want to make the most of out your trip and have more time in each place, buy the JR pass and travel with the Shinkansen. this way you would make a day-long trip by bus into a 3-4h trip. This is worth it because there's just SO MUCH to see in Japan for just 10 days.
but if money is the main concern and you will travel by bus, don't bother with the JR pass, just take your bus, buy an IC card, put money on it and go travel.
Here's some info on IC cards for you:
(if the link above doesn't work, try copying it and pasting in your browser)
I hope this helps!